Patient with left perinephric abcess which does not ruptured have reduced breath sound that is mostly due to plural effusion revealed by CT scan which was sterile. I found this called sympathetic effusion , Why it named as this and what is the mechanism behind it ?
The left perinephric space is adjacent to the left subpleural space so inflammation can spread from the former to the latter.
Diaphragmatic inflammation then results in a left exudative sterile pleural effusion. It's called sympathetic since it's not infective.